Examinando por Autor "Leigh, Nathan"

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    Ítem
    Search for hypervelocity stras in the central regions of the galaxy
    (Universidad Andrés Bello, 2023) Ruiz Fernández, Alonso Luna; Minniti, D.; Rejkuba, Marina; Marchetti, Tommaso; Alonso García, Javier; Leigh, Nathan; Facultad de Ciencias Exactas
    In this thesis, I propose a new approach to search for hypervelocity stars in the inner part of our Galaxy. Hypervelocity stars are moving at velocities around 1000 km s−1 , acquiring such velocity after an interaction with the supermassive black hole at the centre of the Milky Way: Sgr A*. Hence, these stars inform us about i) dynamical stellar interactions with Sgr A*, ii) phenomena in regions with high stellar density, iii) the stellar content in the inner part of the Galaxy, and iv) the presence of massive objects, such as intermediate and stellar-mass black holes. Hypervelocity stars are extremely rare, to identify them it was necessary to characterise the proper motions of the stars in the used catalogues: Gaia , VVV and VIRAC2, which contain hundreds of millions of sources. I explore also different approaches to identify and validate the reliable data in such catalogues, that result in being able to identify the unique objects in these catalogues, in this case, hypervelocity stars. The results of this work are the characterisation of the astrometric data of Gaia DR3 and VIRAC2 with respect to data from the Hubble Space Telescope (HST) in observations towards the Galactic bulge. On one hand, the uncertainties in the proper motions of Gaia DR3 are underestimated with respect to the HST proper motions, thus the need for an inflation factor to bring them into a 1σ consistency. On the other hand, VIRAC2 proper motions are in agreement with HST proper motions. For this reason, I used VIRAC2 proper motions to search for hypervelocity stars. With the developed method, I identified 139 candidate hypervelocity stars in the inner 60 sqdeg. around the Galactic centre. These stars appear to be ejected after an interaction with Sgr A *. Besides that, we identified more than 1000 high-velocity stars (> 600 km s−1 ), probably produced in the Galactic disc, although their origin is uncertain.